This invention relates to a method of producing a water-proofing sheet.
Up to the present, many kinds of water-proofing sheets made of various materials have been used to protect buildings from water. The sheet is adhered on the surface of a foundation such as a concrete roof and so on with an adhesive to constitute a water-proofing layer.
Generally the work is carried out on a foundation dried thoroughly, but sometimes it can not help being carried out on a humid foundation due to the time of work, its relationship with other tasks or the weather.
In such a case, voids appear between the sheet and the foundation by pressure of vapor coming from water contained in the foundation or by expansion of air. Such voids spoil the appearance of the sheet, weaken the strength of adhesion and cause chemical deterioration or fatigue fraction.
In connection with this, there are provided a water-proofing sheet comprising a rubber sheet adhered on a foam rubber sheet which has exhausted grooves on the other side (Japanese Pat. No. 9415/1979). The grooved side of the water-proofing rubber sheet is attached on the surface of a foundation. Then, the vapor and the air coming from the foundation are exhausted out side through the grooves and ventilation holes which are connected thereto.
However, it is complicated and expensive to produce the double layer rubber sheet. Moreover it is difficult to stick the sheets tightly to each other at a joint section to prevent leaking of water.
On the other hand, it was difficult to obtain practical products of the grooved sheet if asphalt is used to make a sheet. Because, conventional rubber asphalts consist of common rubbers and asphalt, they have experienced difficulty in being vulcanized at the high temperature of asphalt processing. When the sheet is put under pressure, the shortage of vulcanization causes its shape to deform and choke the exhaust grooves, and consequently, the exhaustion of the vapor and the air is prevented substantially.